Isolated lissencephaly sequence
Last updated 18 Aug 2020
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Isolated lissencephaly sequence (ILS) is a condition that affects brain development before birth. Normally, the cells that make up the exterior of the brain (cerebral cortex) are well-organized, multi-layered, and arranged into many folds and grooves (gyri). In people with ILS, the cells of the cerebral cortex are disorganized, and the brain surface is abnormally smooth with an absence (agyria) or reduction (pachygyria) of folds and grooves. In most cases, these abnormalities impair brain growth, causing the brain to be smaller than normal (microcephaly). This underdevelopment of the brain causes severe intellectual disability, delayed development, and recurrent seizures (epilepsy) in individuals with ILS.
Description
Isolated lissencephaly sequence (ILS) is a condition that affects brain development before birth. Normally, the cells that make up the exterior of the brain (cerebral cortex) are well-organized, multi-layered, and arranged into many folds and grooves (gyri). In people with ILS, the cells of the cerebral cortex are disorganized, and the brain surface is abnormally smooth with an absence (agyria) or reduction (pachygyria) of folds and grooves. In most cases, these abnormalities impair brain growth, causing the brain to be smaller than normal (microcephaly). This underdevelopment of the brain causes severe intellectual disability, delayed development, and recurrent seizures (epilepsy) in individuals with ILS.
More than 90 percent of individuals with ILS develop epilepsy, often within the first year of life. Up to 80 percent of infants with ILS have a type of seizure called infantile spasms, these seizures can be severe enough to cause brain dysfunction (epileptic encephalopathy). After the first months of life, most children with ILS develop a variety of seizure types, including persisting infantile spasms, short periods of loss of consciousness (absence seizures); sudden episodes of weak muscle tone (drop attacks); rapid, uncontrolled muscle jerks (myoclonic seizures); and episodes of muscle rigidity, convulsions, and loss of consciousness (tonic-clonic seizures).
Infants with ILS may have poor muscle tone (hypotonia) and difficulty feeding, which leads to poor growth overall. Hypotonia also affects the muscles used for breathing, which often causes breathing problems that can lead to a life-threatening bacterial lung infection known as aspiration pneumonia. Children with ILS often develop muscle stiffness (spasticity) in their arms and legs and an abnormal side-to-side curvature of the spine (scoliosis). Rarely, the muscle stiffness will progress to paralysis (spastic paraplegia). Individuals with ILS cannot walk and rarely crawl. Most children with ILS do not develop communication skills.
Inheritance patterns
The source lists the following possible inheritance patterns: X-linked dominant; Autosomal dominant. More than one pattern can apply in different cases.
Related genes
Other names
Classical lissencephaly
ILS
LIS1
Lissencephaly type 1
Lissencephaly, classic
Type 1 lissencephaly
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Further reading and references
- Isolated lissencephaly sequence; MedlinePlus, National Library of Medicine.
- de Wit MC, de Rijk-van Andel J, Halley DJ, Poddighe PJ, Arts WF, de Coo IF, Mancini GM. Long-term follow-up of type 1 lissencephaly: survival is related to neuroimaging abnormalities. Dev Med Child Neurol. 2011 May;53(5):417-21. doi: 10.1111/j.1469-8749.2011.03937.x. Epub 2011 Mar 17.
- Dobyns WB. The clinical patterns and molecular genetics of lissencephaly and subcortical band heterotopia. Epilepsia. 2010 Feb;51 Suppl 1:5-9. doi: 10.1111/j.1528-1167.2009.02433.x. No abstract available.
- Friocourt G, Marcorelles P, Saugier-Veber P, Quille ML, Marret S, Laquerriere A. Role of cytoskeletal abnormalities in the neuropathology and pathophysiology of type I lissencephaly. Acta Neuropathol. 2011 Feb;121(2):149-70. doi: 10.1007/s00401-010-0768-9. Epub 2010 Nov 3.
- Guerrini R, Parrini E. Neuronal migration disorders. Neurobiol Dis. 2010 May;38(2):154-66. doi: 10.1016/j.nbd.2009.02.008. Epub 2009 Feb 23.
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- Spalice A, Parisi P, Nicita F, Pizzardi G, Del Balzo F, Iannetti P. Neuronal migration disorders: clinical, neuroradiologic and genetics aspects. Acta Paediatr. 2009 Mar;98(3):421-33. doi: 10.1111/j.1651-2227.2008.01160.x. Epub 2008 Dec 16.
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